Authorities say a quarter of the forests on both islands have been incinerated, along with habitats of rare plants and animals. The blazes have not reached coastal resorts popular with European tourists.

Environmentalists call the fires a catastrophe.

About 9,000 people were in emergency shelters on Tenerife Wednesday,while most of the 5,000 displaced people on Gran Canaria have begun returning home.

Tenerife authorities say they suspect arsonists started the wildfire on the island. Police on Gran Canaria are holding a forest worker who confessed to starting a fire there last Friday.